FTIR and millimeter wave investigation of the 7 and 9 states of formic acid HCOOH and HCOOH

High resolution FTIR spectra of the two overlapping bands ν₇ and ν₉ of the ¹³C species of formic acid have been measured and analyzed. Rotational transitions in the millimeter wave region were measured and included in the analysis. As in the parent species, there is a strong Coriolis interaction between the 7¹ and 9¹ states. The corresponding IR bands of the parent species have been remeasured and new MMW transitions recorded. The analysis of the spectra for the two species provides an opportunity to consider a reduction of the Hamiltonian employed for the analysis of this type of interacting system of states. Parameters with low correlations could be obtained. Several interstellar features coincide with transitions predicted from these parameters.     

Branches of solutions to semilinear elliptic equations on \mathbb{R}^N

For a large class of functions f, we consider the nonlinear elliptic eigenvalue problem We describe the behaviour of the branch of solutions emanating from an eigenvalue of odd multiplicity below the essential spectrum of the linearized problem. A sharper result is obtained in the case of the lowest eigenvalue. The discussion is based on the degree theory for proper Fredholm maps developed by P.M Fitzpatrick, J. Pejsachowicz and P.J. Rabier. Received November 13, 1996; in final form March 24, 1997     

Template carbon dispersed in polyaniline matrix electrodes: evaluation and application as electrochemical sensors to low concentrations of Cu and Pb

A new electrode, obtained by the dispersion of template carbon nanoparticles onto polyaniline, is presented in this paper. Template carbon was synthesized via the pyrolysis of the polyfurfuryl alcohol inside the nanometric pores of porous Vycor glass, and the electrodes were prepared by a polyaniline-template carbon mixture. Scanning electron microscopy showed that polyaniline-template carbon films presented a wholly modified morphology when compared to polyaniline and polyaniline-graphite films. Electrochemical characterization indicated that the interconversion reactions of polyaniline were strongly facilitated in the presence of the template carbon. The new electrode also exhibited excellent chemical and physical stabilities. Finally, anodic stripping voltammetry measurements revealed that the new electrode presented a noteworthy linear response to very low concentrations of Cu²⁺ and Pb²⁺ ions, under few minutes of pre-concentration.     

Remarks about uniform boundedness of rational points over function fields

We prove certain uniform versions of the Mordell Conjecture and of the Shafarevich Conjecture for curves over function fields and their rational points.

     

The contact problem for a class of orthotropic elastic solids

The contact problem between two orthotropic solids is examined. The problem is solved by using Lodge's method, which permits the transformation of the boundary-value problem of an anisotropic solid to a form identical with the corresponding problem of an isotropic medium. The proposed solution is then compared with known results of certain cases and it is observed that it producesHertz's solution when used for an isotropic case,Lodge's solution when applied to contact between an orthotropic solid and a rigid plane and, finally,Love's solution if the solid is transversely isotropic with the axis of material symmetry perpendicular to the rigid plane of contact.     

Bright,Fluorescent Dyes Based on Imidazo[1,2‐a]pyridines that are Capable of Two‐Photon Absorption

A library of imidazo[1,2‐a]pyridines was synthesized by using the Gevorgyan method and their linear and non‐linear optical properties were studied. Derivatives that contained both electron‐donating and electron‐withdrawing groups at the 2 position were comprehensively investigated. Their emission quantum yield ranged between 0.2–0.7 and it was shown to depend on the substitution pattern, most notably that on the phenyl ring. Electron‐donating substituents improved the luminescence performance of these compounds, whereas electron‐withdrawing substituents led to a more erratic behavior. Substitution on the six‐membered ring had less effect on the fluorescence properties. Extension of the delocalization increased the luminescence quantum yield. A new quadrupolar system was designed that contained two imidazo[1,2‐a]pyridine units on its periphery and a 1,4‐dicyanobenzene unit at its center. This system exhibited a large Stokes‐shifted luminescence that was affected by the polarity and rigidity of the solvent, which was ascribed to emission from an excited state with strong charge‐transfer character. This quadrupolar feature also led to an acceptable two‐photon absorption response in the NIR region.     

Functionalised multi-walled carbon nanotubes-modified electrode for sensitive determination of Diuron in seawater samples

ABSTRACT

This work was focused in to develop an electroanalytical method based on a direct modification of a glassy carbon electrode (GCE) by the deposition of successive aliquots of diluted dispersions of functionalised carbon nanotubes (MWCNT-COOH) in ethanol (0.1 mg.mL^?1) aiming the determination of Diuron into seawater samples, a common antifouling substance, using differential pulse voltammetry as electroanalytical technique. The GCE/MWCNT-COOH showed a sensitivity of 2.20 μA/μmol L^?1 about 10 times higher than the unmodified counterpart (GCE) which showed a sensitivity of 0.192 μA/μmol L^?1. The limits of detection and quantificationwere 6.88 × 10^?8 and 2.29 × 10^?7 mol L^?1 for GCE/MWCNT-COOH while for GCE were 7.87 × 10^?7 and 2.62 × 10^?6 mol L^?1, respectively. The applicability was evaluated with spiked detectable amounts of Diuron into seawater samples. The recovery results were between 76% and 119%.